Hypothalamus, Pituitary and Pineal Gland Flashcards
Hypothalamic hormones (5)
1* Growth hormone releasing hormone (GHRH)
Stimulates GH and somatotrophs
2* Somatostatin
inhibits GH secretion and TSH (by reducing TSH feedback)
Inhibits insulin, glucagon, gastrin, secretin, and VIP
3* Prolactin inhibiting hormone (PIH) – dopamine
Inhibits prolactin (so does GABA)
*Corticotropin releasing hormone (CRH)
Stimulates ACTH, Angiotensin II and is potentiated by ADH
Inhibited by oxytocin
4* Thyrotropin releasing hormone (TRH)
5* Gonadotropin releasing hormone (GnRH)
Stimulates LH and FSH surges: Low-frequency = FSH release. High-frequency = LH
Posterior pituitary, the “neurohypophysis”
Antidiuretic hormone (ADH), or vasopressin
Oxytocin
- Hypopituitarism-
2. Causes: the “nine I’s”:
- Decreased or absent secretion of pituitary hormones
2. Invasive- Space occupying lesions Infarction – Sheehan postpartum hemorrhage Infiltrative - Sarcoidosis (Iron overload) Injury – Severe head trauma Immunologic - Autoimmune Iatrogenic – Medical procedures Infectious – Syphilis, TB Idiopathic - ??? Isolated – Genetic deficiency
Pathology: Pituitary Hyper-secretion
*TQ
Most common cause: Prolactinoma (Infertility or menstrual changes for women)
2nd most common: Growth Hormone tumor
Acromegaly
3rd most common: ACTH pituitary tumors
Cushing Disease
Prolactin agonists
Stress Hypoglycemia High levels of exercise Dietary meats Breast stimulation TRH-(ex.hypothyroidism) Sleep Estrogen Melatonin Glycyrrhiza Rauwolfia Phenothiazines Opiates Opioid peptides β-endorphin MAO inhibitors
Prolactin antagonists
Free T3 & T4 Vitex agnus castus Vitamin B6 Magnesium Cortisol Progesterone Lycopus virginicus
***Dopamine*** (Remember) PGE-1 GABA Acetylcholine (choline) Somatostatin Bromocriptine
Pathology: Prolactin excess
- Functional excess: suspect if high E/P ratio, assumed as opposed to diagnosed
- Medication induced: Tricyclic antidepressants, opiates, haloperidol, Cannabis, Glycyrrhiza, reserpine, OCPs
- Prolactinoma: small tumor usually presenting with galactorrhea and amenorrhea – referral to endocrinologist and co-management – more soon
Diagnostics: serum prolactin and cranial MRI
Functions of growth hormone
Essential for growth in childhood Excess causes acromegaly in adults Has anabolic effects (via insulin-like growth factor) Stimulates thymus hormone release Stimulates gluconeogenesis Decreases glucose uptake and clearance Acts as an insulin antagonist Increases sweating
Growth hormone’s potential benefits
Mediated mainly through IGF-1 and IGFBP-3 increases lean muscle mass decreases percent body fat decreases abdominal fat deposition increases the general sense of well-being increases energy lowers cholesterol increases bone density improves short-term memory
GH agonists
Deep sleep Fasting Insulin overdose hypoglycemia Exercise High protein meals Arginine, ornithine Estrogen Potassium Dopamine Alpha adrenergic agonists Beta adrenergic antagonists
GH antagonists
Cortisol Glucocorticoids Progesterone Fatty acids Obesity Leptin Hypothyroidism Hyperthyroidism Hyperglycemia
GH measurement
GH levels can be indirectly measured by testing for Insulin-like growth factor (IGF-1), also known as somatomedin-C.
IGF-1 is a polypeptide hormone that is produced in the liver in response to GH.
Pathology: GH Deficiency
Congenital “Dwarfism”
Decreased birth length and low growth rate
Short stature, increased fat mass, elevated cholesterol secondary to decreased GH stimulated lipolysis
Acquired Hypothalamic-pituitary tumor – usually noticeable later in life Transient GH deficiency in adolescence Irradiation CNS trauma
Treatment: GH Deficiency
Treatment:
Somatropin
Indications: GH deficiency, children with growth failure, AIDS wasting or cachexia, treatment of short bowel syndrome
**Adverse effects (Know This): edema, arthralgia, elevated A1c, gynecomastia, nausea, otitis media, acne, headaches, hypertension…
Currently toted as “anti-aging” therapy for adults, yet is prohibited by US Federal Law if patients do not have GH deficiency.
Pathology: GH Excess
*Congenital “Gigantism” or Acromegaly (Increases risk of CVD)
Excess GH secretion pre-puberty = gigantism
Excess GH secretion post-puberty = acromegaly
Secondary to a tumor or McCune Albright syndrome
*Presentation includes: Large hands Course feature Thick fingers and toes Large jaw and forehead New onset diabetes Hypogonadism Thyromegaly
